Does finding the conditional and reversing and negating it then selecting the answer choice with the conditional that matches either the original conditional or its contrapositive work every time to find the right answer on sufficient assumption questions? (I hope that I am making sense) I think I've uncovered the SA quesitions, but I need some verification.

No, it does not work every time. Some sufficient assumption questions do not have any conditionals. But I'd be happy to take a look at any questions from any prep tests and talk about how this concept applies to any individual questions.